1. Field of The Invention
The present invention relates to current servo amplification/control apparatus and method for a reversible DC motor which are applicable to a vehicular four-wheel steering (4WS) system with a correction of a motor counter-electromotive force (or back-electromotive to force )generatcd by the rotating DC motor for a terminal (effective) voltage across the motor taken into consideration and without a detection of a current flowing through the DC motor and a motor current feedback circuit.
2. Description of Background Art
A previously proposed current servo amplification/control apparatus which is to be applied to a vehicular motor-driven four wheel steering system is exemplified by FIG. 1.
FIG. 1 generally shows the previously proposed whole controller used for performing a positioning control for the reversible DC motor 1.
As shown in FIG. 1, the controller includes: a motor positioning control/calculating circuit block 2 which calculates a motor current instruction value I* according to an input motor angular displacement (position) instruction value .theta.* and a feedback motor angular position indicative signal .theta.; and a current servo amplification/control circuit block 8 which controls a motor input current in accordance with the current instruction value I* derived from the motor positioning control/calculating circuit block 2. The current amplification/control circuit block 3 derives the motor current I which is coincident with the current instruction value I* by detecting an actual motor current I from its current detection circuit block 4 and feeding back the detected motor current I from its current feedback circuit block 5.
However, since, in the controller shown in FIG. 1, a triangular waveform generator, a counterclockwise direction rotation circuit, a clockwise direction rotation circuit are needed in the motor current feedback circuit block 5 and the current detection circuit block 4 to detect the actually flowing motor current I is also needed, a cost of manufacturing the previously proposed motor current amplification/control apparatus (the whole controller shown in FIG. 1) becomes expensive.